Internal combustion engines are complex mechanisms which typically provide power to a vast array of machines including, for example, power generation sets, earth working machinery, paving machinery, load transfer carrying machinery and the like. In order to remove excess heat from the engine and to keep the engine operating at its most efficient temperature, a cooling and lubricating system is used to provide coolant and lubricant, respectively, to the engine.
Typical cooling systems include air and liquid cooling systems, with liquid cooling systems being most important to larger engines which power heavy machinery and the like. In liquid cooling systems, an array of passages throughout the engine including the cylinder block and head are provided. These cooling passages allow coolant to cool such engine parts as the combustion chamber, cylinder walls, and valve seats and guides, and ensures that the engine is operating at the most efficient temperature.
Similar to the coolant system, lubricating systems also include several passages throughout the engine, but instead provides lubricants, such as oil to the cylinder chamber, engine bearings and other locations. With respect to the cylinder chamber, the oil lubricates and cools the piston so as to decrease the friction between the piston and cylinder. Also, without lubricant, the engine may seize due to increased temperature resulting from the increased heat resulting from friction between the piston and cylinder wall.
Gaskets are typically provided at the cylinder head joint (between the cylinder head and block) in order to safeguard against leakage of fluids, and more specifically to prevent coolant, oil and the like from contaminating each other and being contaminated with other fluids. As a further benefit, gaskets assist in maintaining a proper operating pressure within the combustion chamber. Typical gaskets are made of steel, copper, graphite and fibrous materials; however, due to the thermal cycling of the engine during heating and cooling periods, the gaskets have to be elastomeric so as to adapt to the expansion and contraction of the engine during such heating and cooling periods.
It is not uncommon for gaskets, and especially cylinder head gaskets, to fail (e.g., "blowout", "wear" or become "loose") during the natural thermal loading of the engine. In the case of gasket seal failure, the gaskets typically fail at the weakest point which is the thinnest area between adjacent cylinders and the like. The failure (e.g., cracking, burning and the like) of the gasket may lead to contamination of fluids, such as, for example, coolant entering the crankcase or cylinder and mixing with the engine oil or combustion gases. This will dilute the engine oil and thus accelerate the wear of the engine. If enough coolant leaks into a cylinder, it may even "hydrolock" the engine.
It is further noted that the sealing of the cylinder head joint is particularly important in high compression diesel engines. This is because many high compression diesel engines employ flanged cylinder liners which may complicate the sealing of the cylinder head to the cylinder block. In engines which employ flanged cylinder liners, a spacer plate or plates are provided in the cylinder head joint between the cylinder head and block so as to evenly distribute the high unit loadings throughout the cylinder block and to further avoid associated crack initiation where the flange of the cylinder liner engages the cylinder block. The spacer plate or plates further provide a clearance for the flange of the cylinder liner to be mounted on the cylinder block in the cylinder head joint which eliminates the need for a counter bore in the cylinder block. This counter bore may contribute to an increase in crack initiation in the cylinder block.
In current diesel engines that employ flanged cylinder liners and spacer plates, gaskets clamped between the cylinder block and spacer plate and between the spacer plate and cylinder head are required. These gaskets appear to adequately seal across the cylinder head joint, but nevertheless can be subject to leakage due to thermal loading during engine expansion and contraction cycles. Thus, in these systems, the coolant is capable of leaking into the cylinder and contaminating the oil and other gases. This, of course, may result in reduced efficiency of the engine.
As a result of these problems, several gaskets have been developed in an attempt to improve sealing between the cylinder head and cylinder block. For example, U.S. Pat. No. 5,603,515 to Bock (February 1997) discloses a cylinder head sealing system with removable engine sealing gaskets. In particular, Bock discloses a thermally conductive sealing system for the cylinder head joint of an internal combustion engine comprising a spacer plate clamped in direct contact between the cylinder head and the cylinder block and a plurality of discrete fluid gaskets disposed across the spacer plate and clamped between the cylinder head and cylinder block. Although the Bock system provides an adequate sealing system, in case of failure of any one of the discrete gaskets during thermal loading, coolant or air may enter the cylinder compartment and contaminate the engine oil and gases therein. This would reduce the efficiency of the engine.
By way of further examples, several gasket manufacturers also have developed gaskets having increased sealing capabilities. Some of these manufactures have manufactured a near zero leakage sealing gasket which may be discrete elastomeric gaskets permanently retained in opposing grooves of a metal or plastic retainer. These systems may provide for improved sealing, but in case of gasket failure coolant or other fluids may still enter the cylinder compartment and mix with the engine oil and gases.
In attempting to solve the leakage problem posed by failed seals and gaskets, fluid leakage paths have also been machined within the cylinder head and/or cylinder block. However, these machined passages contribute to an increase in crack initiation in the cylinder block. Thus, in some instances, the use of machined fluid leakage paths within the cylinder head and/or cylinder block lead to a catastrophic failure of the engine.
The present invention is directed to overcoming one or more of the problems as set forth above.